Today, the first locomotive. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.

Think about the word you used
for a train when you were a child -- the word
choo-choo. Choo-choo was the noise made by
steam leaving the cylinders, which were mounted
down by the wheels. If you've never seen that in
real life, you have seen it in movies. A conductor
shouts, All aboard,
steam gushes about the wheels, and the train starts
to move. That choo-choo sound reflects two ideas
that converged around 1800, after steam engines had
been in use for a hundred years. One was the idea
of running steam engines at high pressure; the
other idea was using them for transportation.

The first steam car was made in 1769, before Watt,
by French military engineer Nicholas Cugnot. Most
steam engines were then huge
two-story structures. So it's not surprising
that Cugnot's car was a brute. It carried four
people at two miles per hour. It was meant to pull
field artillery, but it was clumsy and cumbersome.

In 1784, William Murdoch, who worked for Watt, used
a Watt engine to produce a better car -- lighter
and faster. Watt opposed using steam for
transportation. He patented the idea only so he
could put it on ice. Nor did he like the idea of
high-pressure steam, and that's what you
ultimately needed for a vehicle. High pressures
were dangerous.

Early steam engines all depended to some extent on
condensing steam to create a vacuum. Steam not only
pushed the piston out of the cylinder. It also
sucked the piston into the cylinder as it
condensed. Engines were so large because
low-pressure steam took up space. When pressure
reached fifty or a hundred pounds per square inch,
engines could be a lot smaller.

Late eighteenth-century precision boring mills
finally made tight-fitting high-pressure pistons
possible. Cornish inventor Richard Trevithick and
American millwright Oliver
Evans both made high-pressure engines just
after 1800. So it finally made sense to fit a steam
engine into a vehicle. Instead of condensing steam
to create a vacuum, builders simply blew spent
steam into the atmosphere -- making that choo-choo
sound.

Trevithick and Evans both used their engines to
drive primitive cars. Then Trevithick realized he
could use steam to replace the horses that drew
carts on England's rail system. He made the first
successful locomotive in 1804. In 1808, he ran a
little closed-circuit demonstration railroad in
London -- a sort of carnival ride with a locomotive
called the Catch-me-who-can. It moved at a
swift twelve miles per hour. After that, steam
railways spread like ivy, with America close on
British heels.

But we were more rash than the English. We drove
steam pressures up; and across the land we went.
The familiar choo-choo sound of spent steam was, in
fact, the sound of new ideas. And the idea of
eliminating condensation -- of wasting part of
steam's motive force -- was what it took to bind a
sprawling continent together.

I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.

(Theme music)

For the story of Evans and the high-pressure engine,
see, e.g., Pursell, C.W., Jr. Early Stationary
Steam Engines in America: A Study of the Migration of
a Technology. Washington, D.C.: Smithsonian
Institution Press, 1969.

For more on Richard Trevithick, see, e.g., Derry,
T. K., and Williams. T. I. A Short History of
Technology, New York: Oxford University Press,
1960, 1975.

Lardner, The Rev. Dionysius. The Steam Engines
Familiarly Explained and Illustrated, with
additions and notes by James Renwick, LL.D.
Philadelphia: Carey and Hart, 1836.